In the NCI-sponsored Prostate Cancer Prevention Trial (PCPT), initial findings from a decade ago showed that the drug finasteride significantly reduced the risk of prostate cancer, but among those who did develop prostate cancer, paradoxically, the drug was associated with an increased risk of high-grade disease. New findings reported in NEJM on August 15, 2013, based on follow-up of trial participants for up to 18 years, showed that survival of the men on finasteride was equivalent to men who did not take the drug and the reduction in risk of prostate cancer persists. Among nearly 19,000 eligible men who underwent randomization, prostate cancer was diagnosed in 10.5 percent of those in the finasteride group and 14.9 percent of those in the placebo group, a 30 percent reduction in risk. For the men diagnosed with prostate cancer, 10-year survival from time of diagnosis was equivalent between study groups overall (78 percent), in those with low-grade cancers (82 percent), and in those with high-grade cancers (73 percent) providing reassurance that the small excess of higher grade tumors in the men in the finasteride arm of the study did not translate into an increased risk of death.

Previous studies based on the original 2003 analysis had already suggested that the increase in high-grade disease may have been due to prostate gland shrinkage and increased sensitivity in detecting higher grade cancers. In fact, the PCPT was not designed specifically to address the question of high-grade disease. Since 2011, drugs such as finasteride have had to carry a warning that they may increase the risk of high-grade prostate cancer; they have never been approved for the prevention of the disease. Specifically, there was concern that the increase in high-grade cancers detected among men receiving finasteride would result in more deaths. This new analysis was undertaken, in part, to understand if such concern was warranted.